Printing cylinder and a method of producing the same



June 19, 1962 H. G. MEESE ET AL 3,039,389

PRINTING CYLINDER AND A METHOD OF PRODUCING THE SAME Filed Dec. 12, 1958 jm emam' HEINZ GUNTER "GEES-E,

mum nnsiosuusmonng UERMER HOTDP BY: MM 7% United States Patent 3,039,389 PRINTING CYLINDER AND A METHOD OF PRQDUCING THE SAlVfE Heinz Giinter Meese, Erwin Masjoshusmann, and Werner Hotop, all of Dortmund-Aplerbeck, Germany, assignors t0 Deutsche Edelstahlwerke Aktiengesellschaft, Krefeld, Germany Filed Dec. 12, 1958, Ser. No. 779,949 Claims priority, application Germany Dec. 21, 1957 15 Claims. (Cl. 101-378) The invention relates to a printing cylinder for mounting magnetizable flexible stereos of the kind having a ferromagnetic layer on their backs and for rotary printing. Such stereos may be produced for instance of rubber or with a rubber layer incorporating a ferromagnetic powder in the rubber mass or by the insertion of a wire mesh of ferromagnetic material. The invention also relates to a method of producing the cylinder. Cylinders for this purpose require to have a surface magnetized by permanent magnets for magnetically holding the flexible stereos. It has been proposed to make these cylinders by inserting permanent magnet bars into grooves milled longitudinally into a soft iron cylinder in such manner that one pole of each permanent magnet bar is in contact with the floor of its groove, the permanent magnet bars being inserted into the grooves with the interposition of non-ferromagnetic insertions between the walls of the grooves and the bars. A cylinder can be built up in this way with a surface having a plurality of poles of sequentially alternating polarity, one pole being formed by the permanent magnet material and the other by the lands on the soft iron cylinder which separate neighbouring grooves.

To ensure that the stereo will be fixedly held the cylinder surface must have a large number of very closely adjacent poles. Maximum adhesive effect will then be confined to the immediate neighbourhood of the surface. This is essential for mounting the stereos because the magnetizable layer on the back of the stereos must of necessity be rather thin so that it can accommodate only those lines of force which will directly pass longitudinally through the layer. If the number of poles is reduced and the spacing of the poles on the adhesion face thereby increased, then the magnetic field will have too great a penetrative effect. The majority of the lines of force will pass perpendicularly through the magnetizable layer at the back of the stereo and thus fail to contribute to producing adhesive power.

Functionally, these magnetic printing cylinders have been a success in practice, but they have the drawback of being rather expensive as a result of the manner in which they are made. It has also been found that the insertion of the magnet bars occasionally gives rise to difiiculty because the relatively long pre-magnetized bars refuse to slide easily along the slots.

The present invention contemplates the provision of a permanent magnet printing cylinder which is especially simple and convenient to build and which is also distinctly superior in its holding effect to prewously proposed cylinders.

The cylinder according to the present invention is particularly reliable operationally and comprises a support and an assembly of magnet elements forming the cylinder stereo holding surface and comprising soft iron bars with plate-shaped magnets applied thereto, said elements being arranged in adjacency around the axis of the support, and interengaging profiles on the support and the said elements holding the elements on the support. The support may comprise a cylindrical core, interengaging profiles on the core and the said bars holding the elements on the core. The said magnet plates are preferably of an oxidic permanent magnet material.

The method according to the invention employs a support comprising ring guides and soft iron bars secured to plate magnets and adapted to co-operate with said ring guides, and consists in moving said bars in sequence around said ring guides in such a manner that the outer edges of the said bars will present circumferentially spaced alternating longitudinal north poles and south poles on the cylinder surface.

The support may comprise a cylindrical core with ring guides thereon, eg of V-section or dovetail section protfile and of a non-magnetizable material such as an austenitic steel. Soft iron bars of a section adapted to the diameter of the cylinder are pushed on to these profiles, magnet plates preferably of an oxidic permanent magnet material, preferably of type ferric oxide barium oxide in isotropic or anisotropic form, having been afiixed to the bars by cementing them on to the same. All the bars may have a taper section to permit their being placed in close gapless juxtaposition around the periphery of the cylinder. However, in practice it has been found that only some of the bars actually need have a taper section. The magnet plates are magnetized across their shortest dimension either before or after being cemented into position. The soft iron bars are suitably recessed to fit r on to the profiles. The soft iron bars with the permanent magnet plates applied thereto are placed in position in such a way that the soft iron bars which form the pole bars will on the cylinder surface constitute an alternating succession of north poles and south poles. As it is simpler to produce rectangular permanent magnet plates which are small in relation to the size of the individual bar it is preferred to cement a plurality of such plates side by side on to the soft iron bar. The plates are located in such a way that the edge of the soft iron bar on the cylinder face will project above the plates by a few millimetres. Non-ferromagnetic preferably brass, bars are inserted into the recesses thus formed and soldered or cemented into position. In other words, the peripheral face of the cylinder will be formed by soft iron bars alternating with brass bars. It would be possible to fill these gaps with a plastic but if the cylinder face is exposed to considerable wear or to higher temperatures, this may not be advisable. The soft iron bars thus prepared are magnetized, as has been mentioned, in the direction of the shortest dimension of the permanent magnet plates before they are placed in position on the core of the cylinder. The direction of magnetization is such that one half of the bars will have south poles and the other half north poles adjacent the cemented face of the permanent magnet plates. Oppositely polarised bars are then pushed in alternationon to the profiles on the cylinder core, this procedure being continued until the entire circumference of the cylinder is entirely covered with soft iron and non-magnetic bars without anywhere leaving a gap. When all the soft iron bars are thus in position around the perimeter of the cylinder, each bar will be magnetically energised by like poles of two sets of magnets.

If the cylinder diameter is considerable, it is advisable to use a hollow tubular core preferably of non-ferromag netic material to achieve a reduction in weight. This tubular core may then likewise be provided with several profiled guide rails of non-magnetic material which encircle the periphery of the tube and engage corresponding recesses in the soft iron polarised bars.

Thetube may then be mounted on the shaft of the printing cylinder shaft by means of a flange at each end, preferably formed integrally with the tube and likewise consisting of a non-ferromagnetic material, said flanges at the same time forming end members which close the tube ends, and which may be made fast on the shaft for instance by means of a key or a locking pin.

The cylinder according to the invention and the metho employed for constructing the same will now be described with reference to an illustrative example shown in the accompanying drawings in which- FIG. 1 is a perspective view of the cylinder according to the invention, with some of the soft iron bars in position,

FIG. 2 is a partial longitudinal section of the same cylinder,

FIG. 3 is a soft iron magnetic bar ready for insertion into the cylinder,'and

FIG. 4 is the bar shown in cross section.

In FIG. 1 shaft 1 is connected with a cylindrical tube 2 consisting preferably of a non-ferromagnetic material, such as brass, by means of two flanged bushings 3 and 3, preferably integrally formed with the tube and likewise consisting of a non-ferromagnetic material. The tube 2 carries V-section (dovetail) profiled rings 4 of non-magnetic material on to which the magnet elements comprising taper-sectioned soft magnetic bars 5 can be pushed. As shown in FIGS. 2, 3 and 4 a row of rectangular permanent magnet plates 6 of oxidic permanent magnet material is cemented in side by side arrangement on to the soft magnetic bars 5 in such manner that one edge of the permanent magnets is slightly set back by a few millimetres from the adhesion face of the cylinder. The recesses thus formed are filled by the insertion of filler bars 7 consisting of non-ferromagnetic material, preferably brass, which are afiixed to the soft iron bars by solder or by cement. The bottom edges of the bars are provided with V-shaped (dovetail) recesses 8 which fit over the section of the profiled rings 4. The permanent magnet plates are magnetized across their shortest dimension either before or after having been cemented into position, but in any event before the magnet elements are pushed on to the cylinder.

FIG. 4 illustrates one of the magnet elements having a bar which has a taper cross section. A few bars of taper section are included in the assembly on the cylinder, the remaining bars being simply rectangular, so that over the entire surface of the cylinder there will be closely spaced adjacent bars of sequentially opposite polarity. In view of the described arrangement each bar will be magnetically energised by the poles of two rows of permanent magnets of like polarity.

To prevent the tube from working loose on its shaft it is secured thereto by a key 9.

What We claim is:

1. A printing cylinder for supporting a magnetizable flexible stereo, comprising a support and an assembly of magnet elements forming the cylindrical stereo-holding surface, said elements comprising soft iron bars with plate-shaped magnets magnetized across their thickness applied thereto, certain of said magnet elements having the north pole of the magnet at the interface between the magnet and the soft iron bar and the remainder having the south pole at the said interface, said elements being alternately arranged in adjacency around the axis of the support so that the longitudinal edges of the said bars at the said stero-holding surface present alternatring band-like north and south poles therein, said support and the said elements having co-operating interengaging profile means holding the elements on the support.

2. A printing cylinder according to claim 1 in which said plate-shaped magnets are of oxidic permanent magnet material.

3. A printing cylinder according to claim 1 in which the magnet elements each comprise a said soft-iron bar and at least one said plate-shaped permanent magnet of oxidic permanent magnet material bonded to one face of the said bar.

4. A printing cylinder according to claim 1, in which said elements are formed with a longitudinal recess between the outer margin of the soft iron bar and the adjacent edge of the plate-shaped magnets and this recess i contains at least one non-magnetic insert bar so that the stereo-holding cylindrical surface comprises circumferentially spaced longitudinal band-like pole areas formed by the outer edges of the soft iron bars and the spacing non-magnetic bars.

5. A printing cylinder according to claim 1, in which the core comprises a tube provided at its periphery with non-magnetic ring guides, said tube comprising flanged end bushings and a shaft being arranged in said bushings, said magnet elements having profiled portions co-operating with said ring guides, said ring guides and said profiled portions constituting said co-operating interengaging profile means.

6. A magnet element for use in making a support according to claim 1, comprising a rectangular band or bar of soft iron and a plurality of rectangular plates of oxidic permanent magnet material magnetized across their thickness attached facially to one side face of the said band or bar side by side along the'said face so as to form a recess between one longitudinal edge of the said band or bar and the adjacent edges of the said plates, the faces of the said band or bar tapering towards one longitudinal edge of the said band or bar.

7. A magnet element according to claim 6 in which the said recess contains non-magnetic material bonded in place.

8. A printing cylinder for supporting a magnetizable flexible stereo, comprising a core, an assembly of separate elements forming a stereo holding cylindrical surface, said elements each comprising a soft iron bar with at least one plate-shaped magnet magnetized across its thickness attached thereto, certain of said magnet elements having the north pole of the magnet at the interface between the magnet and the soft iron bar and the remainder of the elements having the south pole at the said inter-face, said magnets being set away from a longitudinal edge of the corresponding bar, said elements being arranged alternatively in adjacency around said core so that the longitudinal edges of said bars at the said stereo-holding surface present alternating spaced band-like north and south poles therein, at least some of said elements being of tapering form, and the said core and the said bars having co-opcrating interengaging profiles holding the elements on the core.

9. A printing cylinder according to claim 8, in which the said profiles on the core are constituted by ring zones of non-magnetic material and the said profiles on the soft iron bars radially interlock with said ring zones.

10. A printing cylinder according to claim 8 in which the said profiles on the core are constituted by projecting rings of dovetail section and of non-magnetic material and the said profiles on the soft iron bars comprise cooperating dovetail recesses.

11. A printing cylinder for supporting a magnetizable flexible stereo, comprising a core and an assembly of separate elements, each said element comprising a soft iron bar with a number of plate-shaped permanent magnets magnetized across their thickness bonded thereto so as to form a longitudinal recess between the outer margin of the said bar and the adjacent edge of the plates and a non-magnetic filler in said recess, certain of said elements having the north pole of the magnet rat the interface between the magnet and the soft iron bar and the remainder of the elements'having the south pole at said interface, said elements each comprising said bar, magnet plates and filler being arranged alternately in adjacency around the said core in non-magnetic relation thereto, said core having a circumferentially extending means co-operating with means on said elements to guide said elements in assembly and radially retain them about the core, the outer edges of said soft iron bars presenting alternating circurnferentially spaced longitudinal band-like north and south pole areas separated by said non-magnetic fillers and forming with said fillers a cylindrical stereo-holding surface.

12. The method of producing a printing cylinder employing a support comprising ring guides and soft iron bars secured to plate magnets and adapted to co-operate with said ring guides, and which consists in registering notched regions of said bars with ends of said guides and moving said bars in sequence to engage and move around said ring guides in such a manner that the outer edges of the said bars will present circumferentially spaced alternating longitudinal north poles and south poles on the cylinder surface.

13. The method of producing a printing cylinder for supporting a magnetizable flexible stereo which consists of assembling about a core a multiplicity of magnet elements each comprising a soft iron bar and at least one permanent magnet plate applied thereto, by successively assembling first an element with one pole at the interface between the bar and the plate and then an element with an opposite pole .at the interface between the bar and the plate; guiding said elements in circular movement round the said core and bringing the elements into close adjacency so that the outer edges of the soft iron bars References Cited in the file of this patent UNITED STATES PATENTS 516,885 Barr Mar. 20, 1894 652,112 Jacobus June 19, 1900 1,531,492 Marquardt Mar. 31, 1925 1,657,287 Trist Jan. 24, 1928 1,976,230 Kato Oct. 9, 1934 2,774,302 Stromrne Dec. 18, 1956 FOREIGN PATENTS 963,828 Germany May 16, 1957 1,004,521 France Nov. 28, 1951 

